Answer: C)
Explanation: Options that are missing are:
A.Plows needed for gold and silver mines destroyed native grasses.
B.The cutting down of timber for gold and silver mines led to a decrease in forests.
C.Wreckage from gold and silver mines polluted the supplies of drinking water.
D.Fences needed for gold and silver mines limited the movement of wild game.
The clean and drinking water was polluted with the supplies and dirtness that was falling into the water because of the ones who were digging the gold and silver mines and that was one of situations that have affected American Indians back then.
Water was important to them and their lives and it was a big issue because the water wasn't drinkable anymore.